Are %20 and + the same in a http url?

I know that %20 and + both decode to the same binary value (a space), and for most webservers, especially those that map to physical files they will point to the same resource.

But my question is, must a url like http://www.example.org/hello%20world point to the same resource as http://www.example.org/hello+world, are they canonically the same?

In HTTP/1.0 + didn't map to a space, so I'm specifically asking about HTTP/1.1.